FIG. 1 and FIG. 2 show the cross-sectional views of embodiments of substrates for LSI (large scale integrated circuit), which are directly loaded with LSI chips. Such substrate for carrying LSI chips can be prepared in the following manner. An electrical conductor 3 is laminate-bonded onto the adhesive layer 2 of an epoxy resin-impregnated glass cloth sheet 1 by means of heated rollers, etc., and a copper foil of the electrical conductor 3 is then chemically etched to form a predetermined circuit. If desired, through-holes having electrical conductivity may be optionally formed. Subsequently, LSI chips 4 are placed and bonded by means of an adhesive 5 for die bond, and LSI chips 4 are then connected to the circuit by means of bonding wires 6 to form a module.
As adhesives conventionally used for such substrates for carrying LSI chips, there are known epoxy-novolak resins, nitrile-phenol resins, nylon-epoxy resins, polyester resins, acrylic resins. As circuit designs have been highly complicated in recent years, it has been demanded to provide high-performance adhesives having more higher reliability, particularly adhesives which have scarcely fluidity during the course of copper cladding and exhibit high adhesion between the substrate and copper foil under high-temperature conditions.
Further, adhesives having flame retardance in addition to the above-described characteristics have been required from the viewpoint of safety of electrical apparatuses. To obtain flame-retarded adhesives, flame-retardant fillers or flame-retardant resin components singly or in combination have been conventionally used. However, there is a problem that when the flame-retardant fillers are blended, a lowering in the adhesion of metallic foil is caused. Further, there are problems that when the flame-retardant resin components are used, heat-resistance is generally lowered and a lowering in adhesion between the substrate and the metallic foil under high-temperature conditions is caused.
Epoxy resin-impregnated glass cloth sheets are already known as substrates for carrying LSI chips. However, it is demanded to provide epoxy resin-impregnated glass cloth sheets which have more higher reliability and are excellent in heat resistance and flame retardance.
The present inventors have eagerly made studies to solve the above-mentioned problems associated with the prior art and found that the above-mentioned problems can be solved by providing an adhesive layer comprising a specific curable epoxy resin composition on an epoxy resin-impregnated glass cloth sheet formed by impregnating glass cloth with a specific curable epoxy resin composition and curing it.